Electrical grid-powered aeration is used in most pond-based systems and equalization basins at activated sludge wastewater treatment plants to provide the mixing and oxygenation that enables bacteria to digest organicmatter. Oxygen also is needed in the near-surface water of all ponds and basins to provide an ''odor cap'' by oxidizing malodorous sulfur compounds, preventing their release to air. Much more aeration typically is needed to mix than oxygenate the wastewater. This imbalance causes an operational inefficiency in that grid-power is used to supply more oxygen than needed. The U.S. Environmental Protection Agency concluded that the use of solar-powered circulation (SPC) technology reduces the need to aerate, operational costs, and greenhouse gas emissions associated with electrical power generation. However, the Agency did not quantify electrical, water quality, or other parameters. The New Hampshire Department of Environmental Services directed a 3-site study to quantify the ability of SPC to replace some or all aeration while maintaining good effluent water quality. Water quantity and quality, odor event, and kilowatt-hour consumption and expenditure data were collected 1 year prior to, and 2 years during, SPC treatment at pond-based treatment plants in Pittsfield and Exeter, and at the activated sludge treatment plant in Rochester. Final effluent water quality was maintained, no effluent violations or odor events occurred, and sludge buildup was minimal during the SPC study period. Electricity usage and costs declined by about 38% in Pittsfield and Exeter, and by about 87% in Rochester, resulting in carbon dioxide emission reductions of 273,161, 918,183, and 1,082,509 kg, respectively. Payback periods ranged from 1.9 to 3.7 years. SPC improved operational efficiency at the plants by reducing grid-power consumption while operational objectives were met. The 25-year expected lifetime of SPC units with minimal maintenance requirements indicated long-term reductions in operational expenses and greenhouse gas emissions.

POtable water stOrage tanks are a necessary part of water distribution systems, providing pressure and enough supply for daily and emergency use. but awwa estimates 65 percent of Us storage tanksthat's more than 200,000 tanks-have water quality problems. these problems-common in chlorine and chloramine systems, warm or cold climates-range from temperature stratification, stagnation, dead zones, and short-circuiting to biofilm buildup, loss of residual, nitrification events, and, in northern climates, ice damage.Chlorine systems commonly experience loss of residual and rapid bacteria growth,

Potable water storage tanks in chloraminated systems endure water quality problems, particularly during warm weather. A simple approach can solve these problems, enhance a facility's mixing system, and save money. is president and CEO of SolarBee (www.solarbee.com), Dickinson, N.D.

A Georgia county is winning the battle with blue‐green algae (cyanobacteria) on its surface water supply through near‐surface circulation. Circulators paid for themselves in three years, cut the need for chemicals, restored water quality and the natural food chain, and eliminated taste‐and‐odor issues for potable water customers.

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